The call here is to of course allow the disadvantage from going prone. If I'm belly-crawling, I present a target maybe a foot tall, vs 5+ feet tall. However...I'd also rule as the DM that any hit on a prone character crawling towards the oncoming fire is going to be double damage, because if it hits you, it likely hits you in the head. :)
The player gets the benefit of the rule (which also does make sense IRL, no meta-gaming necessary), but suffers an also very plausible penalty if it goes bad, and a penalty that the rules say nothing about one way or the other (as far as I recall).
The call here is to of course allow the disadvantage from going prone. If I'm belly-crawling, I present a target maybe a foot tall, vs 5+ feet tall. However...I'd also rule as the DM that any hit on a prone character crawling towards the oncoming fire is going to be double damage, because if it hits you, it likely hits you in the head. :)
The player gets the benefit of the rule (which also does make sense IRL, no meta-gaming necessary), but suffers an also very plausible penalty if it goes bad, and a penalty that the rules say nothing about one way or the other (as far as I recall).
There are no rules about hit locations in 5E at all.
I'd argue this is the same as making the IMHO bad rule call that the attackers don't get disadvantage, because it's a bad faith penalty enacted in reaction to a perfectly reasonable tactic. If we start adding "well, it'll do more damage because it hits you in the head..." calls, then the logical progression is to determine what effect helmets have, and if they have one, how much does a helm cost? Which suits of armor come with one included? Is an open-faced helm different from a closed face helm in these circumstances...
It's a slippery slope. Plus there's already a penalty: half of your movement to get back on your feet. Furthermore, in the same vein of "ranged attackers have disadvantage to attack when in melee," the rule of "drop prone = disadvantage against ranged attacks" is meant to be a simple abstraction of why (as one poster mentioned above) "Get DOWN!" is what trained combatants do when they are under fire. It's a viable strategy in combat because it's a reasonable way to abstract a situation that has too many variables to add to 5E's rules. And it's perfectly usable AGAINST the players, too ;-P
Ultimately it's the DM's call, always, but consideration needs to be taken for all the possibilities here, and in my estimation, whenever an argument "could go either way," it's best to leave the rule alone because there's always a chance it interacts with other rules in a carefully balanced system.
I'd argue that it's a slope, but it's not a slippery one :)
If a character is poking his head through a hole in a wall that only his head can fit through, to see what's on the other side, I'd feel pretty okay with double damage on a hit from the guy waiting on the other side with an ax. Now, I'd certainly tell the player that before they made their decision. But I doesn't seem unreasonable to me. I mean, if someone is being executed and the guillotine blade comes down, I'm not rolling for damage. :)
You're right, there is nothing about hit locations. Nothing saying I cannot make that ruling either. And it's a reasonable ruling to make, imo. Because I don't care if you have a helmet or not, your head is more vulnerable than other body parts, even if equally armored. That is a plausible claim (ask football players, whose heads are more armored).
I wouldn't object to a game where that didn't happen. But I wouldn't feel bad about making it happen either.
I think the original question/issue was about springing a homebrew rule on a player in the middle of combat, not looking for additional homebrew rules to add to it. 5e was designed to be simple. I'm not against homebrew at all, but if I joined a group and the DM handed me a second handwritten notebook with "house rules because realism" on it I would say thanks but no thanks.
I think the original question/issue was about springing a homebrew rule on a player in the middle of combat, not looking for additional homebrew rules to add to it. 5e was designed to be simple. I'm not against homebrew at all, but if I joined a group and the DM handed me a second handwritten notebook with "house rules because realism" on it I would say thanks but no thanks.
You're right, that was the original question. When I answered it, I thought I'd say something else related too, as part of the conversation.
I wouldn't play in a game with a notebook of extra rules either. But I have never minded when DMs make rulings where the RAW leave the opening. That's all I'm talking about. Player says "I'm gonna stick my head through that hole." I say "Okay. If you do that, and you get hit on the head, it'll be double damage, because you're basically putting your defenseless head out there for anything to happen." Then let the player choose.
The rules of 5e are quite simplified in part because they didn't want to bog us down in tons of rules, and they didn't want to try to anticipate everything that would happen. IMO, a good DM makes the story believable by making those calls when they happen. If things were flipped, the player was on the other side, and setup a trap for a less intelligent monster, and it stuck its head through the hole in the wall, and the player hit it...and I went with RAW and the player did 1 point of damage, I don't think that would go over well with a lot of players I know. :)
I mean, maybe we know different kinds of players :) I think I am definitely in the minority in some ways. If I fall off the back of a dragon flying 1 mile in the air, with no way to slow my fall, I'm just handing the DM my character sheet, or hoping someone has a way to bring me back from the dead. Because I'm not going to look at the (ridiculous) falling damage rules and think that I actually lived from a 1 mile fall. Some players would demand falling damage RAW. That's fine. Me? I just died.
Totally agree. But if I were your player, I would just ask that 3/4 cover apply and I get my +4 to AC. (If I actually decided I still needed to stick my head though.) But the situations that happen out of combat are always easier to discuss/digest than rule changes in the middle of combat. It's like the other player in a chess game all of the sudden moving their pawns like queens in the middle of the game because they felt like it. (Or for any reason, really.)
Totally agree. But if I were your player, I would just ask that 3/4 cover apply and I get my +4 to AC. (If I actually decided I still needed to stick my head though.) But the situations that happen out of combat are always easier to discuss/digest than rule changes in the middle of combat. It's like the other player in a chess game all of the sudden moving their pawns like queens in the middle of the game because they felt like it. (Or for any reason, really.)
You rules lawyer you! LOL, Kidding. No, I would be fine with the AC bonus in that case. You're not being held in place, you can try to pull your head out, so AC bonus, absolutely. But if you're hit...it's in the head. (Compared to being actually restrained in a guillotine...I'm not giving you a 3/4 cover bonus from the dropping blade :)
How it would actually happen for games I run would be the player saying "I'm going prone and crawling towards them", me saying "Okay, they're at disadvantage. But if you're hit, it'll be double damage." Then the player might say "Wait wait, but (insert other factor here", which I'll listen to, and we'll come to some sort of understanding that keeps us all enjoying the game. (For example "Wait, I have that mithril dwarven helm from the king, my head is my most armored spot!" Okay, cool, no double damage :) But I don't see it as 'changing' a rule in combat, because there is no existing rule about hit locations. It would be the DM establishing what would happen in a place where the rules seem to give discretion. Changing a rule flat out isn't kosher. Unless it leads to everyone having more fun. :)
The last time there was a rule about hit locations was way back in 2nd edition. But even then, it wasn't that it did extra damage, it did specific damage to specific areas. Arms, legs, etc had individually tracked HP if you used the optional rules in the fighter's handbook. (If memory serves... it's been a while.)
I say this because D&D has always had a rule for being hit in the head or other critical areas: the critical hit/nat 20. (Not arguing at all about your ruling, just throwing it out there.)
And yes, guilty as a rules lawyer, but I blame 3.5 for that. (My rehabilitation in 5e has mellowed the rules lawyering out.)
Like many people, I only have rules lawyer tendencies when they will clearly help me out of a bind. :)
We always used a homebrew (stolen from another rpg) hit location table in 1st and 2nd eds--where was 2nd ed's hit location rule? In one of the leatherettes? Oh, wait. There was one in the Fighter's Handbook, wasn't there? 2nd Ed standard rules was the first mention of critical hits, but those aren't synonymous, right? A critical hit doesn't have to be a hit in a critical area, it could be a critical hit in a 'normal' area. After a horrific experience with Runequest, I was always suspicious of being able to inflict damage to specific body parts. We had one RQ fight where our party of 5 was reduced to 1 arm...total, across all 5 of us. Yeesh.
Yeah, it was in the Fighter's Handbook. (Was actually able to find my old dusty copy.) The were all kinds of extra rules like critical hits, followed by critical hit confirmation rolls, location rolls, etc. And yes, critical hits don't have to be in specific areas, but when my players roll 20s, especially if it deals a ton of damage or kills an enemy, I will describe the hit as hitting a vital area, usually head/neck/etc. Just easier to explain why it does so much damage.
But... we're close to hijacking at this point from the original question of changing rules in the middle of combat.
Goblins are bunkered in behind a 3ft tall wall and open fire on them with short bows. My more "rules lawyer" player has a bright idea and decides to drop prone and belly crawl ...... on the flat, unobstructed, stone floor, TOWARDS the bunkered in goblins who are 25ft away. He quotes to me from the PHB where it says "...... going prone gives disadvantage to attackers...... blah blah. Yeah he gets shot anyways because I decide that rule in this situation is silly. Player goes nuts and gets insistent ".... the book CLEARY says..." Give me your thoughts on this please.
Yeah... you messed up. The tactic seems valid, the rules were in his favor, you handled it poorly, and you derogatorily called a good player a 'rules lawyer'... in a rules lawyers forum... populated by rules lawyers.
You could've just told him: "Sure, but crawling on the flat, unobstructed, stone floor will also give the goblins advantage due to the circumstance... they're in a pretty sweet spot". DM's are free to hand out advantage for circumstances (that too is in the rules).
Have fun is the main rule to abide by here. It sounds like between DM and "rules lawyer" there is enough conflict to eliminate, or at least jeopardize, the fun. The truth is you gotta either find common ground or suffer through it. There is nothing wrong with forcing the goblins to withdraw, add some reinforcements or allow the goblins to toss grenades from behind full cover!
essentially your plan was never going to survive contact, so be supportive of the players actions and react to what they do rather than hold them to what you had planned. I guarantee you will all have more fun that way.
DM’s changing the rules in the middle of an action is poor DM’ing.
Players expect the DM to have read the rule book as well as the players.
Houserules are ok and should be laid out before the session.
After a DM get’s outsmarted by a player, the DM can change ruling as he wants. Let the player use his brain, and call a houerule after.
Its not the first time nor it will be the last. In the end the DM has the final word. Let’s see how many players will be at his table and how many continue playing in his game with sunglasses to please their own egos.
Some players continue playing although some rules are bent and brocken by DM’s, in that case i consider they wear sunglasses ;) and they continue playing to satisfy their own desires (i can understand that)
DM’s changing the rules in the middle of an action is poor DM’ing.
Players expect the DM to have read the rule book as well as the players.
Houserules are ok and should be laid out before the session.
After a DM get’s outsmarted by a player, the DM can change ruling as he wants. Let the player use his brain, and call a houerule after.
Its not the first time nor it will be the last. In the end the DM has the final word. Let’s see how many players will be at his table and how many continue playing in his game with sunglasses to please their own egos.
While in this situation I think the DM is in the wrong, I don't think players should have the goal of outsmarting the DM. The players should describe the to the DM what they are trying to accomplish and the methods by which they want to accomplish that goal while the DM should adjudicate.
DM’s have a tough job and we sometimes make mistakes. We try to learn from them.
As a player, I understand why the situation described in the OP is so annoying but DM’s will always have the final say. It’s the nature of the game and we have to move on.
I think that a DM needs to have the attitude that the customer (player) is always right and a player needs to have the attitude that the boss (DM) is always right.
If both sides give a little, any disagreements can be solved and everyone can get back to having fun.
Totally agree. But if I were your player, I would just ask that 3/4 cover apply and I get my +4 to AC. (If I actually decided I still needed to stick my head though.) But the situations that happen out of combat are always easier to discuss/digest than rule changes in the middle of combat. It's like the other player in a chess game all of the sudden moving their pawns like queens in the middle of the game because they felt like it. (Or for any reason, really.)
You rules lawyer you! LOL, Kidding. No, I would be fine with the AC bonus in that case. You're not being held in place, you can try to pull your head out, so AC bonus, absolutely. But if you're hit...it's in the head. (Compared to being actually restrained in a guillotine...I'm not giving you a 3/4 cover bonus from the dropping blade :)
How it would actually happen for games I run would be the player saying "I'm going prone and crawling towards them", me saying "Okay, they're at disadvantage. But if you're hit, it'll be double damage." Then the player might say "Wait wait, but (insert other factor here", which I'll listen to, and we'll come to some sort of understanding that keeps us all enjoying the game. (For example "Wait, I have that mithril dwarven helm from the king, my head is my most armored spot!" Okay, cool, no double damage :) But I don't see it as 'changing' a rule in combat, because there is no existing rule about hit locations. It would be the DM establishing what would happen in a place where the rules seem to give discretion. Changing a rule flat out isn't kosher. Unless it leads to everyone having more fun. :)
I say this because D&D has always had a rule for being hit in the head or other critical areas: the critical hit/nat 20. (Not arguing at all about your ruling, just throwing it out there.)
This, at least in part, and definitely in this situation, is why you don't need a "ok, if you stick your head out, you get +4 AC from 3/4 cover, but if you get hit, you'll take double damage" house rule. By raising your AC, you're making critical hits more likely, compared to regular hits. When you consider that being hit on the head should not always result in double damage (the blow might glance off your skull, or merely nick an ear, for example), then it all falls into place: stick your head out, you're less likely to be hit, but if you are hit, it's more likely to be a critical hit.
While it may seem backwards and/or illogical that a larger proportion of hits would be critical hits when your AC is higher, bear in mind that the frequency with which you'll be hit will still be smaller. Critical hits have a flat 5% (2.5% with Disadvantage, 9.75% with Advantage) chance of occurring. Regular hits have a chance that depends on both the attack bonus and the AC, and, naturally, have a lower chance of occurring when the AC goes up, assuming the attack bonus stays the same. For example, for an AC of 11, with an attack bonus of +1, a hit will occur on rolls of 10 through 20 (11 rolls, for a probability of 55%), and critical hits will occur on rolls of 20 (5% chance). The probability a hit is a critical hit, given that the attack hits, is roughly 9.1% (out of the 11 possibilities for hits, one is a critical, so 1/11 ~= 9.1%). On the other hand, for an AC of 15, given the same attack bonus of +1, a hit will occur on rolls 14 through 20 (7 rolls, for a probability of 35%), and critical hits will still occur on rolls of 20 (5% chance). The probability a hit is a critical hit, given that the attack hits, is roughly 14.3% (out of the 7 possibilities for hits, one is a critical, so 1/7 ~= 14.3%). So by raising your AC by 4, you decreased the chance you'd be hit from 55% to 35%, the chance you'd be critically hit remained at 5%, but you increased the chance you'd be critically hit given that you were hit from ~9.1% to ~14.3%. So basically, a guy with 10 Dexterity, clad in leather armor, sticking his head out, will be hit significantly less often than one out in the open, but if he is hit, the chance he'll be critically hit goes up by ~47% (from ~9.1% to ~14.3%).
TL;DR: you don't have to implement rules like "sticking your head out from cover or going prone makes you less likely to be hit, but more likely to be critically hit if you're hit", because the game's basic rules already do that for you, for free. :D
This, at least in part, and definitely in this situation, is why you don't need a "ok, if you stick your head out, you get +4 AC from 3/4 cover, but if you get hit, you'll take double damage" house rule. By raising your AC, you're making critical hits more likely, compared to regular hits. When you consider that being hit on the head should not always result in double damage (the blow might glance off your skull, or merely nick an ear, for example), then it all falls into place: stick your head out, you're less likely to be hit, but if you are hit, it's more likely to be a critical hit.
While it may seem backwards and/or illogical that a larger proportion of hits would be critical hits when your AC is higher, bear in mind that the frequency with which you'll be hit will still be smaller. Critical hits have a flat 5% (2.5% with Disadvantage, 9.75% with Advantage) chance of occurring. Regular hits have a chance that depends on both the attack bonus and the AC, and, naturally, have a lower chance of occurring when the AC goes up, assuming the attack bonus stays the same. For example, for an AC of 11, with an attack bonus of +1, a hit will occur on rolls of 10 through 20 (11 rolls, for a probability of 55%), and critical hits will occur on rolls of 20 (5% chance). The probability a hit is a critical hit, given that the attack hits, is roughly 9.1% (out of the 11 possibilities for hits, one is a critical, so 1/11 ~= 9.1%). On the other hand, for an AC of 15, given the same attack bonus of +1, a hit will occur on rolls 14 through 20 (7 rolls, for a probability of 35%), and critical hits will still occur on rolls of 20 (5% chance). The probability a hit is a critical hit, given that the attack hits, is roughly 14.3% (out of the 7 possibilities for hits, one is a critical, so 1/7 ~= 14.3%). So by raising your AC by 4, you decreased the chance you'd be hit from 55% to 35%, the chance you'd be critically hit remained at 5%, but you increased the chance you'd be critically hit given that you were hit from ~9.1% to ~14.3%. So basically, a guy with 10 Dexterity, clad in leather armor, sticking his head out, will be hit significantly less often than one out in the open, but if he is hit, the chance he'll be critically hit goes up by ~47% (from ~9.1% to ~14.3%).
TL;DR: you don't have to implement rules like "sticking your head out from cover or going prone makes you less likely to be hit, but more likely to be critically hit if you're hit", because the game's basic rules already do that for you, for free. :D
I see what you're saying, and I think it's kinda like that. But a character with a big enough to hit bonus could hit you without critting. I'd be saying that any hit would be a crit regardless of roll. It's a smaller 'benefit' than without the AC bonus, but still significant. But I get where you're coming from. :)
There's a reason people shout "GET DOWN" in a live-fire situation.
The call here is to of course allow the disadvantage from going prone. If I'm belly-crawling, I present a target maybe a foot tall, vs 5+ feet tall. However...I'd also rule as the DM that any hit on a prone character crawling towards the oncoming fire is going to be double damage, because if it hits you, it likely hits you in the head. :)
The player gets the benefit of the rule (which also does make sense IRL, no meta-gaming necessary), but suffers an also very plausible penalty if it goes bad, and a penalty that the rules say nothing about one way or the other (as far as I recall).
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I'd argue that it's a slope, but it's not a slippery one :)
If a character is poking his head through a hole in a wall that only his head can fit through, to see what's on the other side, I'd feel pretty okay with double damage on a hit from the guy waiting on the other side with an ax. Now, I'd certainly tell the player that before they made their decision. But I doesn't seem unreasonable to me. I mean, if someone is being executed and the guillotine blade comes down, I'm not rolling for damage. :)
You're right, there is nothing about hit locations. Nothing saying I cannot make that ruling either. And it's a reasonable ruling to make, imo. Because I don't care if you have a helmet or not, your head is more vulnerable than other body parts, even if equally armored. That is a plausible claim (ask football players, whose heads are more armored).
I wouldn't object to a game where that didn't happen. But I wouldn't feel bad about making it happen either.
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I think the original question/issue was about springing a homebrew rule on a player in the middle of combat, not looking for additional homebrew rules to add to it. 5e was designed to be simple. I'm not against homebrew at all, but if I joined a group and the DM handed me a second handwritten notebook with "house rules because realism" on it I would say thanks but no thanks.
You're right, that was the original question. When I answered it, I thought I'd say something else related too, as part of the conversation.
I wouldn't play in a game with a notebook of extra rules either. But I have never minded when DMs make rulings where the RAW leave the opening. That's all I'm talking about. Player says "I'm gonna stick my head through that hole." I say "Okay. If you do that, and you get hit on the head, it'll be double damage, because you're basically putting your defenseless head out there for anything to happen." Then let the player choose.
The rules of 5e are quite simplified in part because they didn't want to bog us down in tons of rules, and they didn't want to try to anticipate everything that would happen. IMO, a good DM makes the story believable by making those calls when they happen. If things were flipped, the player was on the other side, and setup a trap for a less intelligent monster, and it stuck its head through the hole in the wall, and the player hit it...and I went with RAW and the player did 1 point of damage, I don't think that would go over well with a lot of players I know. :)
I mean, maybe we know different kinds of players :) I think I am definitely in the minority in some ways. If I fall off the back of a dragon flying 1 mile in the air, with no way to slow my fall, I'm just handing the DM my character sheet, or hoping someone has a way to bring me back from the dead. Because I'm not going to look at the (ridiculous) falling damage rules and think that I actually lived from a 1 mile fall. Some players would demand falling damage RAW. That's fine. Me? I just died.
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Totally agree. But if I were your player, I would just ask that 3/4 cover apply and I get my +4 to AC. (If I actually decided I still needed to stick my head though.) But the situations that happen out of combat are always easier to discuss/digest than rule changes in the middle of combat. It's like the other player in a chess game all of the sudden moving their pawns like queens in the middle of the game because they felt like it. (Or for any reason, really.)
You rules lawyer you! LOL, Kidding. No, I would be fine with the AC bonus in that case. You're not being held in place, you can try to pull your head out, so AC bonus, absolutely. But if you're hit...it's in the head. (Compared to being actually restrained in a guillotine...I'm not giving you a 3/4 cover bonus from the dropping blade :)
How it would actually happen for games I run would be the player saying "I'm going prone and crawling towards them", me saying "Okay, they're at disadvantage. But if you're hit, it'll be double damage." Then the player might say "Wait wait, but (insert other factor here", which I'll listen to, and we'll come to some sort of understanding that keeps us all enjoying the game. (For example "Wait, I have that mithril dwarven helm from the king, my head is my most armored spot!" Okay, cool, no double damage :) But I don't see it as 'changing' a rule in combat, because there is no existing rule about hit locations. It would be the DM establishing what would happen in a place where the rules seem to give discretion. Changing a rule flat out isn't kosher. Unless it leads to everyone having more fun. :)
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The last time there was a rule about hit locations was way back in 2nd edition. But even then, it wasn't that it did extra damage, it did specific damage to specific areas. Arms, legs, etc had individually tracked HP if you used the optional rules in the fighter's handbook. (If memory serves... it's been a while.)
I say this because D&D has always had a rule for being hit in the head or other critical areas: the critical hit/nat 20. (Not arguing at all about your ruling, just throwing it out there.)
And yes, guilty as a rules lawyer, but I blame 3.5 for that. (My rehabilitation in 5e has mellowed the rules lawyering out.)
Like many people, I only have rules lawyer tendencies when they will clearly help me out of a bind. :)
We always used a homebrew (stolen from another rpg) hit location table in 1st and 2nd eds--where was 2nd ed's hit location rule? In one of the leatherettes? Oh, wait. There was one in the Fighter's Handbook, wasn't there? 2nd Ed standard rules was the first mention of critical hits, but those aren't synonymous, right? A critical hit doesn't have to be a hit in a critical area, it could be a critical hit in a 'normal' area. After a horrific experience with Runequest, I was always suspicious of being able to inflict damage to specific body parts. We had one RQ fight where our party of 5 was reduced to 1 arm...total, across all 5 of us. Yeesh.
Looking for new subclasses, spells, magic items, feats, and races? Opinions welcome :)
Yeah, it was in the Fighter's Handbook. (Was actually able to find my old dusty copy.) The were all kinds of extra rules like critical hits, followed by critical hit confirmation rolls, location rolls, etc. And yes, critical hits don't have to be in specific areas, but when my players roll 20s, especially if it deals a ton of damage or kills an enemy, I will describe the hit as hitting a vital area, usually head/neck/etc. Just easier to explain why it does so much damage.
But... we're close to hijacking at this point from the original question of changing rules in the middle of combat.
Yeah... you messed up. The tactic seems valid, the rules were in his favor, you handled it poorly, and you derogatorily called a good player a 'rules lawyer'... in a rules lawyers forum... populated by rules lawyers.
You could've just told him: "Sure, but crawling on the flat, unobstructed, stone floor will also give the goblins advantage due to the circumstance... they're in a pretty sweet spot". DM's are free to hand out advantage for circumstances (that too is in the rules).
Have fun is the main rule to abide by here. It sounds like between DM and "rules lawyer" there is enough conflict to eliminate, or at least jeopardize, the fun. The truth is you gotta either find common ground or suffer through it. There is nothing wrong with forcing the goblins to withdraw, add some reinforcements or allow the goblins to toss grenades from behind full cover!
essentially your plan was never going to survive contact, so be supportive of the players actions and react to what they do rather than hold them to what you had planned. I guarantee you will all have more fun that way.
Jesus Saves!... Everyone else takes damage.
DM’s changing the rules in the middle of an action is poor DM’ing.
Players expect the DM to have read the rule book as well as the players.
Houserules are ok and should be laid out before the session.
After a DM get’s outsmarted by a player, the DM can change ruling as he wants. Let the player use his brain, and call a houerule after.
Its not the first time nor it will be the last. In the end the DM has the final word. Let’s see how many players will be at his table and how many continue playing in his game with sunglasses to please their own egos.
I mostly agree. I just don't know what the sunglasses thing means :) Is that a reference I'm missing?
Looking for new subclasses, spells, magic items, feats, and races? Opinions welcome :)
Some players continue playing although some rules are bent and brocken by DM’s, in that case i consider they wear sunglasses ;) and they continue playing to satisfy their own desires (i can understand that)
While in this situation I think the DM is in the wrong, I don't think players should have the goal of outsmarting the DM. The players should describe the to the DM what they are trying to accomplish and the methods by which they want to accomplish that goal while the DM should adjudicate.
DM’s have a tough job and we sometimes make mistakes. We try to learn from them.
As a player, I understand why the situation described in the OP is so annoying but DM’s will always have the final say. It’s the nature of the game and we have to move on.
I think that a DM needs to have the attitude that the customer (player) is always right and a player needs to have the attitude that the boss (DM) is always right.
If both sides give a little, any disagreements can be solved and everyone can get back to having fun.
This, at least in part, and definitely in this situation, is why you don't need a "ok, if you stick your head out, you get +4 AC from 3/4 cover, but if you get hit, you'll take double damage" house rule. By raising your AC, you're making critical hits more likely, compared to regular hits. When you consider that being hit on the head should not always result in double damage (the blow might glance off your skull, or merely nick an ear, for example), then it all falls into place: stick your head out, you're less likely to be hit, but if you are hit, it's more likely to be a critical hit.
While it may seem backwards and/or illogical that a larger proportion of hits would be critical hits when your AC is higher, bear in mind that the frequency with which you'll be hit will still be smaller. Critical hits have a flat 5% (2.5% with Disadvantage, 9.75% with Advantage) chance of occurring. Regular hits have a chance that depends on both the attack bonus and the AC, and, naturally, have a lower chance of occurring when the AC goes up, assuming the attack bonus stays the same. For example, for an AC of 11, with an attack bonus of +1, a hit will occur on rolls of 10 through 20 (11 rolls, for a probability of 55%), and critical hits will occur on rolls of 20 (5% chance). The probability a hit is a critical hit, given that the attack hits, is roughly 9.1% (out of the 11 possibilities for hits, one is a critical, so 1/11 ~= 9.1%). On the other hand, for an AC of 15, given the same attack bonus of +1, a hit will occur on rolls 14 through 20 (7 rolls, for a probability of 35%), and critical hits will still occur on rolls of 20 (5% chance). The probability a hit is a critical hit, given that the attack hits, is roughly 14.3% (out of the 7 possibilities for hits, one is a critical, so 1/7 ~= 14.3%). So by raising your AC by 4, you decreased the chance you'd be hit from 55% to 35%, the chance you'd be critically hit remained at 5%, but you increased the chance you'd be critically hit given that you were hit from ~9.1% to ~14.3%. So basically, a guy with 10 Dexterity, clad in leather armor, sticking his head out, will be hit significantly less often than one out in the open, but if he is hit, the chance he'll be critically hit goes up by ~47% (from ~9.1% to ~14.3%).
TL;DR: you don't have to implement rules like "sticking your head out from cover or going prone makes you less likely to be hit, but more likely to be critically hit if you're hit", because the game's basic rules already do that for you, for free. :D
I see what you're saying, and I think it's kinda like that. But a character with a big enough to hit bonus could hit you without critting. I'd be saying that any hit would be a crit regardless of roll. It's a smaller 'benefit' than without the AC bonus, but still significant. But I get where you're coming from. :)
Looking for new subclasses, spells, magic items, feats, and races? Opinions welcome :)